The present invention relates to semiconductor manufacturing. More particularly, the present invention provides capacitor structures including recessed hemispherical grain silicon and methods of forming the same.
In the fabrication of integrated circuits, various conductive layers are used. For example, during the formation of semiconductor devices, such as dynamic random access memories (DRAMs), static random access memories (SRAMs), ferroelectric (FE) memories, etc., conductive materials are used in the formation of storage cell capacitors and also may be used in interconnection structures, e.g., conductive layers of contact holes, vias, etc.
As memory devices become more dense, it is necessary to decrease the size of circuit components forming such devices. One way to retain storage capacity of storage cell capacitors of the memory devices and at the same time decrease the memory device size is to increase the dielectric constant of the dielectric layer of the storage cell capacitor. Therefore, high dielectric constant materials are used in such applications interposed between two electrodes. One or more layers of various conductive materials may be used as the electrode material.
Further, to the increase the capacitance for a storage cell capacitor of a memory device without increasing the occupation area of the storage cell capacitor, various techniques have been used to increase the surface area of the lower electrode of the capacitor. For example, hemispherical grains (HSG) have been used to enhance such surface area of the lower electrode of a capacitor of a memory device.
However, in many cases, the use of HSG to enhance surface area of an electrode can be problematic. The manufacturing of container capacitors, such as is described in U.S. Pat. No. 5,270,241 (Dennison et al.) involves a singulation process whereby the continuous conductive material lining the containers and extending between them on the upper surface of the structure is partially removed to separate the conductive material within a container from the conductive material in the other containers. Singulation may be accomplished using a chemical mechanical polishing (CMP) step which removes only the uppermost horizontal expanses of the continuous conductive layer.
Although CMP is effective at separating the containers, it leaves a structure in which the hemispherical grain silicon precursor layer (i.e., the layer from which the hemispherical grain silicon is formed) and the underlying doped silicon layer both extend to the upper edge of the capacitor plates. As a result, after conversion of the hemispherical grain silicon precursor layer to a layer of hemispherical grain silicon by, e.g., seeding and annealing or any other suitable technique, the hemispherical grain silicon layer typically extends above the outer layer of doped silicon along the edges of the capacitor plates.
Grains or particles from the exposed edge of the hemispherical grain silicon layer are, however, susceptible to separation from the hemispherical grain silicon layer. Once separated or broken off, the loose particles can fall between adjacent capacitors, resulting in electrical shorts between the adjacent capacitors. Such defects adversely affect the output of the manufacturing processes used to form the capacitors. Although typically associated with cup-shaped capacitors, these problems are also experienced in connection with other capacitor structures, e.g., trench, tub, etc.
The present invention provides capacitor structures with edge zones that are substantially free of hemispherical grain silicon along the upper edges of the capacitor structures. The resulting recessed hemispherical grain silicon layers reduce or prevent separation of particles from the hemispherical grain silicon layer during subsequent manufacturing processes, thereby reducing defects and increasing throughput.
The present invention also includes methods of forming the capacitor structures in which the silicon layer used to form the hemispherical grain silicon is selectively removed to provide an edge zone that is substantially free of hemispherical grain silicon.
In one aspect, the present invention provides a capacitor structure including a cavity having a sidewall structure, an opening, and a bottom opposite the opening; a first layer located on an inner surface of the sidewall structure, wherein the first layer is electrically conductive; a second layer located on the first layer, the second layer comprising hemispherical grain silicon; and an edge zone on the inner surface of the sidewall structure proximate the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a capacitor structure including a cavity having a sidewall structure, an opening, and a bottom opposite the opening; a first layer located on an inner surface of the sidewall structure, wherein the first layer is electrically conductive; a second layer located on the first layer, the second layer including hemispherical grain silicon; and an edge zone on the inner surface of the sidewall structure proximate the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity over about 20% or less of the distance between the opening and the bottom of the cavity, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a capacitor structure including a cavity having a sidewall structure, an opening, and a bottom opposite the opening; a first layer located on an inner surface of the sidewall structure, wherein the first layer is electrically conductive; a second layer located on the first layer, the second layer including hemispherical grain silicon; and an edge zone on the inner surface of the sidewall structure proximate the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity and having a depth of about 2000 Angstroms or less from the opening of the cavity, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a capacitor structure including a cavity having a sidewall structure, an opening, and a bottom opposite the opening; a first layer located on an inner surface of the sidewall structure, wherein the first layer includes doped silicon; a second layer located on the first layer, the second layer including hemispherical grain silicon; and an edge zone on the inner surface of the sidewall structure proximate the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a capacitor structure including a cavity having a sidewall structure, an opening, and a bottom opposite the opening; a first layer located on an inner surface of the sidewall structure, wherein the first layer includes doped silicon; a second layer located on the first layer, the second layer including hemispherical grain silicon; and an edge zone on the inner surface of the sidewall structure proximate the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity over about 20% or less of the distance between the opening and the bottom of the cavity, wherein the edge zone is substantially free of the hemispherical grain silicon
In another aspect, the present invention provides a capacitor structure including a cavity having a sidewall structure, an opening, and a bottom opposite the opening; a first layer located on an inner surface of the sidewall structure, wherein the first layer includes doped silicon; a second layer located on the first layer, the second layer including hemispherical grain silicon; and an edge zone on the inner surface of the sidewall structure proximate the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity and having a depth of about 2000 Angstroms or less from the opening of the cavity, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a method of forming a capacitor structure by providing a cavity in a substrate, the cavity having a sidewall structure, an opening, and a bottom opposite the opening of the cavity; providing a first layer on an inner surface of the sidewall structure, wherein the first layer is electrically conductive; providing a second layer on substantially all of the first layer, the second layer including hemispherical grain silicon precursor; providing fill material in the cavity, wherein at least an edge of the second layer is exposed proximate the opening of the cavity; and removing the hemispherical grain silicon precursor in the second layer proximate the opening of the cavity to form an edge zone about the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity; and converting the hemispherical grain silicon precursor in the second layer to hemispherical grain silicon, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a method of forming a capacitor structure by providing a cavity in a substrate, the cavity having a sidewall structure, an opening, and a bottom opposite the opening of the cavity; providing a first layer on an inner surface of the sidewall structure, wherein the first layer includes doped silicon; providing a second layer on substantially all of the first layer, the second layer including hemispherical grain silicon precursor; providing fill material in the cavity, wherein at least an edge of the second layer is exposed proximate the opening of the cavity; and removing the hemispherical grain silicon precursor in the second layer proximate the opening of the cavity to form an edge zone about the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity; and converting the hemispherical grain silicon precursor in the second layer to hemispherical grain silicon, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a method of forming a capacitor structure by providing a cavity in a substrate, the cavity having a sidewall structure, an opening, and a bottom opposite the opening of the cavity; providing a first layer on an inner surface of the sidewall structure, wherein the first layer including doped silicon; providing a second layer on substantially all of the first layer, the second layer including hemispherical grain silicon precursor; providing fill material in the cavity, wherein at least an edge of the second layer is exposed proximate the opening of the cavity; removing the hemispherical grain silicon precursor in the second layer proximate the opening of the cavity by contacting at least the exposed edge of the second layer with an etchant including TMAH at a concentration greater than 2.25% (by weight) to form an edge zone about the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity; and converting the hemispherical grain silicon precursor in the second layer to hemispherical grain silicon, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a method of forming a capacitor structure by providing a cavity in a substrate, the cavity having a sidewall structure, an opening, and a bottom opposite the opening of the cavity; providing a first layer on an inner surface of the sidewall structure, wherein the first layer includes doped silicon; providing a second layer on substantially all of the first layer, the second layer including hemispherical grain silicon precursor; providing fill material in the cavity, wherein at least an edge of the second layer is exposed proximate the opening of the cavity; removing the hemispherical grain silicon precursor in the second layer proximate the opening of the cavity by contacting at least the exposed edge of the second layer with an etchant including TMAH at a concentration greater than 2.25% (by weight) and less than 3% (by weight) to form an edge zone about the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity; and converting the hemispherical grain silicon precursor in the second layer to hemispherical grain silicon, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a method of forming a capacitor structure by providing a cavity in a substrate, the cavity having a sidewall structure, an opening, and a bottom opposite the opening of the cavity; providing a first layer on an inner surface of the sidewall structure, wherein the first layer is electrically conductive; providing a second layer on substantially all of the first layer, the second layer including hemispherical grain silicon; providing fill material in the cavity, wherein at least an edge of the second layer is exposed proximate the opening of the cavity; and removing the hemispherical grain silicon in the second layer proximate the opening of the cavity to form an edge zone about the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a method of forming a capacitor structure by providing a cavity in a substrate, the cavity including a sidewall structure, an opening, and a bottom opposite the opening of the cavity; providing a first layer on an inner surface of the sidewall structure, wherein the first layer includes doped silicon; providing a second layer on substantially all of the first layer, the second layer including hemispherical grain silicon; providing fill material in the cavity, wherein at least an edge of the second layer is exposed proximate the opening of the cavity; and removing the hemispherical grain silicon in the second layer proximate the opening of the cavity to form an edge zone about the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a method of forming a capacitor structure by providing a cavity in a substrate, the cavity having a sidewall structure, an opening, and a bottom opposite the opening of the cavity; providing a first layer on an inner surface of the sidewall structure, wherein the first layer including doped silicon; providing a second layer on substantially all of the first layer, the second layer including hemispherical grain silicon; providing fill material in the cavity, wherein at least an edge of the second layer is exposed proximate the opening of the cavity; removing the hemispherical grain silicon in the second layer proximate the opening of the cavity by contacting at least the exposed edge of the second layer with an etchant including TMAH at a concentration of greater than 2.25% (by weight) to form an edge zone about the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity; and converting the hemispherical grain silicon precursor in the second layer to hemispherical grain silicon, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a method of forming a capacitor structure by providing a cavity in a substrate, the cavity having a sidewall structure, an opening, and a bottom opposite the opening of the cavity; providing a first layer on an inner surface of the sidewall structure, wherein the first layer includes doped silicon; providing a second layer on substantially all of the first layer, the second layer including hemispherical grain silicon precursor; providing fill material in the cavity, wherein at least an edge of the second layer is exposed proximate the opening of the cavity; removing the hemispherical grain silicon precursor in the second layer proximate the opening of the cavity by contacting at least the exposed edge of the second layer with an etchant including TMAH at a concentration greater than 2.25% (by weight) and less than 3% (by weight) to form an edge zone about the opening of the cavity, the edge zone extending from the opening of the cavity towards the bottom of the cavity; and converting the hemispherical grain silicon precursor in the second layer to hemispherical grain silicon, wherein the edge zone is substantially free of the hemispherical grain silicon.
In another aspect, the present invention provides a capacitor including a cavity having a sidewall structure, an opening, and a bottom opposite the opening, the sidewall structure extending between the opening and the bottom of the cavity; a first electrode including an electrically conductive first layer located on an inner surface of the sidewall structure, a second layer including hemispherical grain silicon located on the first layer, and an edge zone on the inner surface of the sidewall structure proximate the opening of the cavity, wherein the edge zone extends from the opening of the cavity towards the bottom of the cavity, and further wherein the edge zone is substantially free of the hemispherical grain silicon; a dielectric layer located on at least a portion of the first electrode; and a second electrode located on the dielectric layer.
These and other features and advantages of the present invention are described below with respect to illustrative embodiments of the apparatus and methods.